Multi-axial bone plate system

ABSTRACT

An orthopedic bone plate system includes a bone plate for placement adjacent one or more vertebral bodies. The system further includes a locking element including a compression member and a fixation member, the compression member having an aperture and a deformable portion. Also included is a bone fastener having a bone engaging portion and a stem portion. The stem is slidably receivable within the aperture of the compression member while the locking member is receivable within an aperture of the bone plate. As the compression member is brought into proximity of a vertebral body along the longitudinal axis of the bone fastener, an increasing force is exerted against the fixation member and translated to the bone plate. The resultant force is translated back to the fixation member to the compression member which causes the deformable portion of the compression member to clamp the bone fastener relative to the bone plate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Application Ser. No.12/961,682, filed on Dec. 7, 2010, which is a divisional of U.S.application Ser. No. 11/175,426, filed on Jul. 6, 2005, the disclosuresof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to an orthopedic implantassembly system and in particular to a multi-axial bone plate system.

Orthopedic implant assembly systems having a multi-axial bone plate areknown in the art and include at least two pedicular screws anchored inadjacent vertebrae to be treated and a connecting plate designed toconnect the screw heads together in a rigid manner. Previous referencesdisclose a system of this kind in which each pedicular screw has ahexagonal section part for inserting the screw into the bone and on topof which is a threaded shank. The plate has a plurality of oblongopenings through which the various threaded shanks can be inserted andan open groove on its bottom face to prevent rotation of the hexagonalpart of each pedicular screw.

Each pedicular screw is associated with a stirrup through which thethreaded shank of the screw also passes and which straddles the top ofthe plate. Finally, a nut is screwed onto the threaded shank to trap andimmobilize the plate with the stirrup on top of it, between it and thehexagonal portion of the screw.

Further, known systems include at least two pedicular screws and aconnecting plate for linking screws together in essentially a rigidmanner. Each screw has a bone anchor threaded part, a non-circularsection head, and a threaded end shank adapted to cooperate with a nut.The plate has at least one opening adapted to have the threaded endshank of the screw pass through it and be trapped between the screw headand the nut. Raised patterns are provided on the top face of the plateand on the bottom face of the stirrup to prevent longitudinal sliding ofthe plate relative to the screw. A locking member is also provided forpreventing relative angular movement between the heads of the screws andthe connecting plate. The locking member is adapted to be insertedbetween the plate and the screw head and includes a bar through whichthe threaded end shank of the screw passes. The locking member furtherincludes a first locking cooperation of shapes with the screw head and asecond cooperation of shapes with the plate.

Although these systems are generally satisfactory, they neverthelesshave certain drawbacks. Specifically, in certain systems, raisedpatterns have to be provided to prevent sliding because the plate andthe stirrup cooperate via two plane faces in compression. Absence of theraised patterns would lead to the risk of entirely unacceptable relativemovement of the vertebrae. The machining required to create these raisedpatterns significantly increases the mean cost of the plates and thestirrups.

Additionally, the raised patterns can impede fine adjustment of thesystem. For example, there are only a particular number of discretemutual positions of the plate and the stirrup, i.e., a particular numberof discrete distances between the screws. Moreover, if the nut isovertightened before the final tightening, lateral sliding of the plateand the stirrup during adjustment may be impeded.

Some of the drawbacks associated with other designs include that thefirst locking cooperation and second cooperation of shapes with theplate forbid and restrict plate movement in an anterior and posteriordirection once the pedicle screw has been rested against the platemember.

Additionally, most plate systems include a bone fastener with a threadedend extended from the vertebral body. In order to lock the screwrelative to the plate, a nut must be used in combination with the screw.The problem associated with this design is that if the screw is notplaced at the correct depth within the vertebral body, the assembly mustbe disassembled in order to either increase or decrease the depth of thescrew in the vertebrae. An additional problem results from this actiondue to the fact that once the screw has been placed too deep within thevertebral body, the screw might be less securely locked within thevertebral body when the screw is backed out and placed in its correctposition.

Other shortcomings of known systems include angled orientations in thesagittal direction are not permitted due to the shape of the lockingcooperation members.

SUMMARY OF THE INVENTION

In accordance with one or more embodiments of the present invention, anorthopedic bone plating system includes a bone plate for placementadjacent one or more vertebral bodies. The bone plate has an apertureextending along a longitudinal axis of the bone plate.

The assembly further includes a locking element having a compressionmember and a fixation member wherein the compression member has anaperture and at least one deformable portion. The assembly is connectedto a vertebral body with the help of a bone fastener having alongitudinal axis. The bone fastener further includes a stem and abone-engaging portion. The stem of the bone fastener may be slidablyreceived within the aperture of the compression member. As the stem isbeing received by the compression member, the compression member may bebrought into proximity of a vertebral body along the longitudinal axisof the bone fastener and create an increasing force which is exertedagainst the fixation member. A resulting force causes the fixationmember to exert a pressure against the bone plate and translate a secondresultant force back through the fixation member to the compressionmember causing the deformable portion of the compression member to clamponto the bone fastener thereby locking the assembly together.

The compression member and fixation member may be separate elementswherein the fixation member includes an aperture for receiving thecompression member. Furthermore, the compression member and fixationmember may have mateable threads which are screwed together as thecompression member is brought into proximately of the vertebral body.

The fixation member may further include a tapered aperture extendingtherethrough. Additionally, the bone fastener may be smooth.

The orthopedic bone plate system may include a channel for receiving thefixation member, which permits the fixation member to slide relative tothe bone plate. The channel being located within the bone plate.Furthermore, the fixation member may include at least one key and thebone plate may include at least one keyway wherein the key may bereceived by the keyway. In at least one embodiment, the keyway may havea height that is greater than the height of the key in order to permitan angled orientation of the fixation member relative to the bone plate.

In an additional embodiment of the present invention, an orthopedic boneplate implant system is provided having a plate member which may beplaced adjacent and along one or more of the vertebral bodies. The platemember includes an aperture extending therethrough. The assembly alsoincludes a split sleeve having a central aperture and a slot extendingfrom an exterior surface of the split sleeve to the aperture. The slotpermits the expansion and contraction of the aperture of the splitsleeve. The split sleeve is sized to be received within the aperture ofthe plate member.

The channel portion may extend substantially the entire longitudinaldirection of the plate and either come to a tapered end or abrupt end.Furthermore, the channel portion itself may also include a guide railthat receives a lateral pin extending from an exterior of the splitsleeve. The lateral pin is placed and dimensioned on the split sleeve tobe received by the guide rail when the split sleeve is placed in thechannel portion of the plate member.

The split sleeve may have two parallel flat walls and two oppositecurved walls.

In one embodiment of the present invention, the parallel flat walls mayinclude the lateral pins of the split sleeve.

The bone fastener may have an end portion that is either smooth,concaved inwards or outwards relative to the vertebral body. The bonefastener may further include a recess for cooperating with the tool. Therecess may be in the form of a hexagon, a slot or various other recessesand projections which can be made into a tool.

A bottom portion of the expansible screw may include at least one slitextending vertically to allow the compression or expansion of a portionof the expansible screw.

Furthermore, the expansible screw may include a ridge which overhangs atleast partly the split sleeve. The ridge may further be defined in thatit has at least two flat surfaces on its sidewall. The split sleeve mayinclude a threaded portion and the expansible screw may include a secondthreaded portion wherein the two threaded portions are able to bescrewed to one another.

In an alternate embodiment, the plate member of the orthopedic input mayinclude slots or ridges. Additionally, the split sleeve may have acentral aperture which has an interior with a greater circumference atthe top of the interior as you get to the bottom of the interior.Furthermore, the expansible screw having an aperture within may includean exterior with a bottom portion angled so as to increase in size.

The method of operation of the present invention may include the stepsof providing a plate member, a bone fastener and a locking element asdescribed herein. The bone fastener may first be engaged to a vertebralbody and then the stem of the bone fastener slidably receiving the platemember and the locking element about its circumference so that the stemis located within the apertures of the plate and the locking elementrespectively. The locking element may include a compression member and afixation member. As the compression member is brought into proximity ofthe vertebral body along the longitudinal axis of the bone fastener, thecompression member causes an increasing force to be exerted against thefixation member which in response places pressure against the platemember until a resultant force is translated back through the twomembers and causes the deformable portion of the compression member toclamp the bone fastener relative to the bone plate.

The method of fixing one or more vertebral bodies in a desiredrelationship may further include adjusting the position of the bonefastener after sliding the plate member over the stem of the bonefastener.

A bone fastener is also included for connecting the plate member to avertebral body. The fastener may include a first end portion engageablewith the vertebral body and a second end portion capable of extendingthrough the aperture of the split sleeve.

A final component of the assembly is an expansible screw having anopening extending therethrough. The opening is sized to receive thesecond end portion of the fastener and further includes a top portionand a bottom portion. The bottom portion of the screw is capable ofexpanding and contracting about a central axis of the screw.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating an embodiment of theorthopedic implant of the present invention implanted in a vertebrae;

FIG. 2 is an exploded perspective view of one embodiment of the systemof the present invention;

FIG. 3 is a sectional view of the embodiment illustrated in FIG. 2partly assembled and taken along line 3-3 in FIG. 2 and viewed indirection of the arrows;

FIG. 4 a is a perspective view of an elongate plate used in oneembodiment of the present invention;

FIG. 4 b is a cross-sectional view of a plate used in one embodiment ofthe present invention;

FIG. 5 is a front perspective view of a bone fastener used in oneembodiment of the present invention.

FIG. 6 a is a perspective view of a split sleeve used in one embodimentof the present invention;

FIG. 6 b is a cross-sectional view of the split sleeve of FIG. 6 a;

FIG. 7 a is a perspective view of an expandable screw used in oneembodiment of the present invention; and

FIG. 7 b is a cross-sectional view of the expandable screw of FIG. 7 a;

DETAILED DESCRIPTION

For the purposes of promoting and understanding the principles of thepresent invention, reference will now be made to the embodimentillustrated in the drawings and specification language will be used todescribe the same. Nevertheless, by those skilled in the art, it will beunderstood that no limitation of the scope of the present invention isthereby intended, and further changes in the illustrated device may bemade without deviating from the scope of the present invention.

As shown in FIG. 1, the spinal implant system 10 of the presentinvention includes a plate 12, an expansible locking screw 16 and a bonefastener 18. As shown in the figures, bone fasteners 18 function toanchor plate 12 to vertebral bodies 2 and may be orientated at an anglewith regard to the vertebral body.

FIG. 2 details the assembly of the parts of FIG. 1 employed in thespinal implant system 10. In a preferred embodiment, the spinal implantsystem 10 includes an elongate member such as plate 12, expansible screw16, bone fastener 18 and split sleeve 14. Although the preferredembodiment illustrated in the figures is shown with only one plate 12and bone fastener 18 and related elements, differing numbers of any ofthese elements may be utilized without departing from the scope of thepresent invention. For example, a plurality of plates 12 can be used inconjunction with each other, or a greater or lesser number of bonefasteners 18 may be used depending upon the configuration of theelongate member, the medical problem to be addressed and/or any otherfactors. The present invention contemplates having at least the sameamount of split sleeves 14, expansible screws 16 and bone fasteners 18.Furthermore, the present invention contemplates each plate 12 will beused with at least a single bone screw 18 and related devices; however,each plate 12 is capable of receiving a plurality of split sleeves 14,expansible screws 16 and bone fasteners 18 without deviating from thescope of the present invention.

Referring now to FIGS. 2, 3, 4 a and 4 b, there is shown a preferredembodiment of plate 12. Plate 12 preferably has a generallyrounded-rectangular or oval shape, an upper surface 30, a lower surface32, a proximal end 31 and a distal end 33. Additionally, plate 12 hastwo opposing sides, right rail 13 and left rail 15. Right rail 13 andleft rail 15 may be substantially mirror images of one another. Plate 12further includes elongate aperture 36 extending along the longitudinalaxis 34 of plate 12 from upper surface 30 to lower surface 32 and fromend 31 to end 33. Elongate aperture has a generally open geometryenabling split sleeve 14, expansible screw 16 and bone fastener 18 to beplaced at any number of axial positions within elongate aperture 36.Elongate aperture 36 generally has a non-uniform geometry about acentral axis 35 which extends perpendicularly to the plane of plate 12.

In a preferred embodiment, right rail 13 and left rail 15 surroundelongate aperture 36 of plate 12 and include an upper wall 38 adjacentto upper surface 30. The geometry of left rail 13 and upper rail 15 ofaperture 36 further include a key way or groove 40 adjacent to upperwall 38 composed of median ceiling 42, median portion 44 and medianridge 46. A lower portion 48 of rails 13 and 15, adjacent to key way 40,includes a lower surface 50 adjacent to lower wall 49 and sidewall 52adjacent to lower ridge 50, concludes the remaining exterior geometry ofelongate aperture 36. In one embodiment, elongate aperture 36 hassubstantially the same geometry extending from the proximal end 31 tothe distal end 33 or the previously mentioned ridge portions and railsmay either abruptly halt or in a preferred embodiment may linearlytransition into a smooth geometry at the distal and proximal ends asshown in FIG. 4 a.

Plate 12 is of sufficient length to bridge more than one vertebrae, asshown in FIG. 1, for which stabilization is required, and it will beappreciated, various dimensions of the plate and its features exist, allwithin the scope of the present invention. For example, the plate 12 maybe substantially planar as shown in FIG. 2 or have a concave shape asshown in FIG. 1.

The plate 12, as well as the other elements of the assembly, ispreferably made from a biologically inert material, for example, anymetal customarily used for surgical devices and particularly those usedfor bone screws and pins, such as titanium or stainless steel. Othersuitable materials include, but are not limited to, alloys, compositematerials, ceramics or carbon fiber materials.

With reference to FIG. 5, there is shown a preferred embodiment of abone fastener 18. Bone fastener 18 is in the shape of a pedicle screw;however, various other fasteners may be utilized including bone hooks.Preferably, bone fastener 18 has a threaded end 152 for anchoring thefastener into a vertebra or similar bone structure and an opposing stemend 150. In a preferred embodiment, stem end 150 is smooth. Bonefastener 18 may further include recess 154 to enable bone fastener 18 tobe screwed into a vertebrae using a screw driver, wrench, alien key orsimilar tool. Recess 154 may be in the form of a hexagon as shown in thefigures or alternatively, may be a slot or other shapes which allow thetools previously mentioned to mate to the bone fastener 18 and screw thebone fastener 18 into a vertebral body. Smooth stem 150 is preferablysized to be able to be slidably received by expansible screw 16,detailed in FIGS. 7 a and 7 b, specifically aperture 124 of expansiblescrew 16 as will be described below. Bone fastener 18 may also includeupper end section 156, which may have a substantially flat end surfacearea as shown in FIG. 5. However, in an alternate embodiment, uppersection 156 may also have a spherical configuration either concave orconvex relative to threaded end 152.

Referring now generally to FIGS. 2, 3, 6 a and 6 b, there is shown apreferred embodiment of a split sleeve 14. Split sleeve 14 may have agenerally rounded-square or oval shape. Split sleeve 14 may include afirst flat side 60, and opposing second flat side 62, a first arcuateside 64 and an opposing second arcuate side 66. Sides 64 and 66 could beof any shape, however, sides 60, 62 preferably permit split sleeve 14 toslide within aperture 36 without rotating. Split sleeve 14 may furtherinclude an upper surface 68 and a lower surface 70 along with aperture72, extending therebetween. Aperture 72 generally has a non-uniformgeometry about central axis 74. The first side 60 and second side 62 mayinclude keys 76 and 78 which engage key ways 40 on rails 13 and 15 ofthe plate 12, respectively. Although a description of only one key willbe detailed with reference to key 76, it should be realized that key 78may be substantially similar to key 76 having all the same features. Key76 protrudes from second side 62 and includes top ledge 80 and lowerledge 82 extending horizontally from second side 62. Side 84 adjacent toboth top ledge 80 and lower ledge 82 extends between the two ledges. Key76 may be sized and located on second side 62 so when split sleeve 14 isplaced into elongate aperture 36 of plate 12, pin 76 is housed withinkey way 40 as defined by side 84. Keys 76 and 78 may have a heightslightly less than the height of key way 40 to permit split sleeve 14 toslide freely along key way 40 of plate 12. Furthermore, the reducedheight of key 76 enables split sleeve 14 to have an angled orientationrelative to plate 12, in the sagittal plane. In the preferredembodiment, keys 76, 78 extend only part way along sides 60, 62 butcould extend the entire length.

Split sleeve 14 further includes through-slot 102 vertically extendingfrom upper surface 68 to lower surface 70. Slot 102 is further definedin that it extends horizontally from the exterior of split sleeve 14 toaperture 72. The outer circumference of split sleeve 14 is substantiallycontinuous except for through-slot 102. Through-slot 102 permits splitsleeve 14 to expand and compress horizontally thereby increasing ordecreasing the diameter of aperture 72. Split sleeve 14 may becompressed about slot 102 to allow insertions of keys 76, 78 into keyway 40.

As previously mentioned, aperture 72 has a non-uniform geometryextending between upper surface 68 to lower surface 70 of split sleeve14. Specifically, inner wall 90 is adjacent to upper surface 68. Innerwall 90 may have a tapered design as shown in FIG. 6B to better receiveexpansible screw 16, as will be described below. A first ridge 92extends from inner wall 90 towards central axis 74, with median wall 94extending downward towards lower surface 70 adjacent to first ridge 92.A second ridge 96 is adjacent to median wall 94 and extends towardcentral axis 74 while lower wall 98 is adjacent to second ridge 96.Inner wall 90 includes threads 91 which may be mated to the threads ofthe expansible screw 16 described herein after. Lower wall 98 mayinclude vertical wall 97 and tapered skirt 99 along with edge 101. Innerwall 90, first ridge 92, median wall 94, second ridge 96 and lower wall98 all combine to define female cone 100.

Split sleeve 14 is placed within elongate aperture 36 of plate 12 whenassembling the spinal implant assembly 10. In this position, lowersurface 70 of split sleeve 14 is rested on or slightly above lower ridge50 of plate 12 and as previously mentioned, pins 76 and 78 are locatedwithin key way 40 at the right rail 13 and the left rail 15 of the plate12. Split sleeve 14 is sized to move freely along plate 12 and permit apossible angled orientation of the split sleeve with respect to plate 12in the sagittal plane. Thus, preferably, the height of split sleeve 14is less than the distance from the upper surface 30, to lower ridge 50.Preferably, in a relaxed state, split sleeve 14 has a width less thanthe distance between opposing rails 13 and 15 of aperture 36 of plate12.

Referring now to FIGS. 7 a and 7 b, there is shown a preferredembodiment of the expansible screw 16. The expansible screw 16 includesupper surface 120, lower surface 122 and aperture 124 extendingtherebetween upper surface 120 and lower surface 122. Expansible screw16 further includes cap section 126 and deflectable male cone section128. Axially extending portion 130 includes threads 131 which areengageable with threads 91 on split sleeve 14. Male cone section 128further includes, extending downward from ridge 132, individual fingers134 with slits 136 therebetween each individual finger 134. Preferably,fingers 134 are tapered inwards so as to be slidably received by lowerwall 90 of split sleeve 14. Male cone 128 of expansible screw 16 isdesigned so as to be able to receive fastener 18 and is geometricallyconstant throughout aperture 124. However, as a force is exertedhorizontally relative to central axis 138 of expansible screw 16, malecone 128 is capable of compressing either inwardly or expandingoutwardly in the same direction of the force applied. Cap section 126 ofexpansible screw 16 includes not only upper surface 120 but also gripsurface 140 and overhang 142 and may also include opposing slots 139 forcooperating with a tool. Furthermore, aperture 124 also extends throughcap section 126 thereby creating a continuous aperture throughexpansible screw 16.

In a method of use, once bone fastener 18 has been coupled with orfastened to a vertebral body, plate 12 along with split sleeve 14 isplaced over smooth stem 150 of bone fastener 18. First split sleeve 14may be placed within aperture 36 of plate 12. Then, by aligning uppersection 156 of bone fastener 18 to aperture 72 of split sleeve 14, splitsleeve 14 and plate 12 are slidably received by stem 150. Since bonefastener 18 is a substantially cylindrical body having a center axis,this alignment may be accomplished by aligning central axis 74 of splitsleeve 14 to the center axis 158 of bone fastener 18. Bone plate 12 andsplit sleeve 14 are then freely moveable in a vertical directionrelative to bone fastener 18 and specifically an anterior-posteriordirection.

In order to lock the various components of the spinal implant assembly10 together, expansible screw 16 must be screwed into split sleeve 14.This is accomplished by first aligning aperture 124 of expansible screw16 with upper section 156 of bone fastener 18. Once again, since stem150 of bone fastener 18 is substantially cylindrical and has a radialcentral axis 158, central axis 138 of expansible screw 16 may be alignedwith the radial central axis 158 of the bone fastener 18.

Aperture 72 of split sleeve 14 is sized so as to be able to acceptexpansible screw 16 and bone fastener 18 at opposing ends. Furthermore,expansible screw 16 engages threads 91 within aperture 72 of splitsleeve 14 and the two are screwed together such that the taperedportions of each engage one another. This causes an outward horizontalforce against split sleeve 14 and an inward force on deflectable fingers134. The fingers 134 grip the stem 156 of the bone fastener 18 as theyare constricted inwards. This is due to the fact that male cone 128 ofexpansible screw 16 is wedged shaped, i.e., having a narrower lowerportion as compared to its upper portion. Through-slot 102 of splitsleeve 14 permits the expansion of split sleeve 14 in the horizontaldirection. As split sleeve 14 is forced to expand, first side 60 beginsto apply pressure against upper wall 38 and lower wall 49 of the plate12. Key 78 may contact median portion 44 of key way 40 located on plate12. Similarly, at the opposing end, second side 62 also applies pressureagainst upper wall and lower wall 49 as well as the fact that key 76 maycontact median portion 44 of guide rail 40 of plate 12. Thus, as ahorizontal force in a direction away from central axis 74 of splitsleeve 14 is placed on the interior of the split sleeve 14, the splitsleeve 14 expands horizontally increasing the size of through-slot 102until the rails 13 and 15 of elongated aperture 36 of plate 12 apply areactive force against the walls of split sleeve 14 thus locking thesplit sleeve in place.

Once split sleeve 14 has reached its maximum expansion capability,further axial movement of expansible screw 16 causes it to lock on toscrew 18. Since expansible screw 16 is further translated downward, andsplit sleeve 14 can no longer expand, the reactive force caused by theplate 12 translated through split sleeve 14 begins to compress fingers134 of expansible screw 16. This causes fingers 134 to constrict aboutsmooth stem 150 of bone fastener 18 locking the bone fastener relativeto the plate.

In a locked position, cap 126 of expansible screw 16, specificallyoverhang 142 of expansible screw 16 may abut upper surface 68 of splitsleeve 14. Thus, male cone 128 is completely housed in aperture 72 ofsplit sleeve 14.

The rotation of expansible screw 16 thus causes the plate to lockrelative to the bone fastener 18. The stem 150 of bone fastener 18 mayhave a smooth surface to allow easy adjustment after plate 12 has beenpositioned and assembled, thus overcoming the disadvantage of threadedend fasteners. The surgeon may easily change the bone screw positionengaged with the vertebrae by loosening expansible screw 16 and slidingthe assembly in either an anterior/posterior direction orinferior/superior direction. Afterwards, the assembly may be lockedagain by tightening expansible screw 16. This avoids the problem ofhaving to disassemble all the elements from one another in order toadjust only certain elements.

Other embodiments not shown in the illustrated figures may includesingle elongated aperture 36 being divided into a plurality of aperturesby cross-members extending between opposing rails 13 and 15 of plate 12substantially perpendicular to longitudinal axis 34. The cross-memberswould have to be sufficiently separated from one another as well as fromproximal end 31 and distal end 33 to permit split sleeve 14, expansiblescrew 16 and bone fastener 18 to be placed within the shortenedapertures and still be locked together relative to plate 12.

Although the present invention herein has been described with referenceto particular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1-27. (canceled)
 28. A method of fixing one or more vertebral bones in adesired relationship, comprising the steps of: a. providing a platemember, a bone fastener and a locking element, said plate member havingan aperture, said bone fastener adapted for connecting said plate memberto the vertebral bone and including a stem, a bone engaging portion anda longitudinal axis, said locking element including a compression memberand a fixation member, said compression member having an hole extendingtherethrough and at least one deformable wall; b. engaging said bonefastener to the vertebral bone; c. sliding said plate member and saidlocking element over said stem of said bone fastener so that said stemis located within said aperture of said plate member and said hole ofsaid compression member; and d. bringing said compression member intoproximity of the vertebral bone along said longitudinal axis of saidbone fastener, wherein as said compression member is brought intoproximity of the vertebral bone increasing force is exerted against saidfixation member, wherein said fixation member exerts a force againstsaid plate member which causes a resultant force to be translated backthrough said fixation member to said compression member causing saiddeformable portion to clamp said bone fastener relative to said platemember.
 29. The method according to claim 28, wherein said compressionmember and said fixation member are separate elements and said fixationmember includes an aperture for receiving said compression member. 30.The method according to claim 28, wherein said compression member andsaid fixation member include threads that engage one another as saidcompression member is brought into proximity of the vertebral bone alongsaid longitudinal axis of said bone fastener.
 31. The method accordingto claim 28, further comprising the step of adjusting a position of saidbone faster after sliding said plate member over said stem of said bonefastener.
 32. The method according to claim 29, wherein said compressionmember and said fixation member include threads that engage one anotheras said compression member is brought into proximity of the vertebralbone along said longitudinal axis of said bone fastener.
 33. The methodaccording to claim 28, further comprising positioning said fixationmember within said aperture of said plate member.
 34. The methodaccording to claim 33, wherein said step of positioning said fixationmember within said aperture of said plate member is performed beforesaid step of sliding said plate member and said locking element oversaid stem of said bone fastener.
 35. A method of fixing one or morevertebrae in a desired relationship, comprising the steps of: a.securing a bone fastener to a vertebral bone, the bone fastener having astem extending along a longitudinal axis; b. positioning the stem of thebone fastener into engagement with a fixation member; c. positioning aplate member proximate the vertebral bone; and d. moving a compressionmember towards the vertebral bone along the longitudinal axis of thestem of the bone fastener, such that the compression member engages thefixation member and causes the fixation member to deform so as to lockthe fixation member with respect to the plate member, and such that thecompression member deforms to clamp the bone fastener.
 36. The method ofclaim 35, wherein the step of moving the compression member towards thevertebral bone includes advancing a threaded portion of the compressionmember along a threaded portion of the fixation member.
 37. The methodof claim 35, wherein the step of positioning the stem of the bonefastener into engagement with the fixation member includes positioningthe stem of the bone fastener through an opening in the fixation member.38. The method of claim 37, wherein the step of moving the compressionmember towards the vertebral bone includes moving the compression memberinto the opening in the fixation member.
 39. The method of claim 35,wherein the plate member includes an aperture.
 40. The method of claim39, further comprising positioning the fixation member within theaperture of the plate member.
 41. The method of claim 40, wherein thestep of positioning the fixation member within the aperture of the platemember is performed before the steps of positioning the stem of the bonefastener into engagement with the fixation member and positioning theplate member proximate the vertebral bone.
 42. The method of claim 40,wherein the aperture in the plate member is elongated along at least aportion of the plate member, the method further comprising sliding thefixation member along the aperture in the plate member.
 43. The methodof claim 42, wherein the deformation of the fixation member so as tolock the fixation member with respect to the plate member includeslocking a position of the fixation member along the aperture in theplate member.
 44. The method of claim 40, further comprising pivotingthe fixation member with respect to the plate member.
 45. The method ofclaim 35, wherein the stem of the bone fastener is received within ahole through the compression member during the step of moving thecompression member towards the vertebral bone along the longitudinalaxis of the stem of the bone fastener.
 46. The method of claim 45,wherein at least a portion of the stem of the bone fastener which isreceived within the hole through the compression member is non-threaded.47. The method of claim 35, further comprising: loosening thecompression member; then moving the plate member with respect to thebone fastener; and then tightening the compression member to lock theplate member with respect to the bone fastener.